1. Field of the Invention
The present invention relates to a shadow mask in a flat Braun tube, more particularly, to a damper wire for a shadow mask in a flat Braun tube for prevention of vibration of the shadow mask occurred by an external vibration.
2. Background of the Related Art
In the flat Braun tube, electron beams emitted from the electron gun pass through electron beam pass through holes in the shadow mask selectively, and hit a fluorescent film surface on an inside surface of a panel, for reproducing a picture by making the fluorescent film surface luminescent. In view of a nature of the shadow mask, the shadow mask is designed to have a radius of curvature corresponding to the panel of the Braun tube. As a related art shadow mask with a spherical panel in a Braun tube has a small radius of curvature following the spherical panel, a shape of the shadow mask itself could have an adequate rigidity against deformation. According to this, the howling was not serious, in which electron beams misland on a screen owing to vibration of the shadow mask caused by an external vibration. However, as the panel becomes flat with an increase of the radius of curvature, the recent shadow mask can not have an adequate rigidity against deformation identical to the related art shadow mask having a smaller radius of curvature. According to this, the howling becomes serious owing to the external vibration, which deteriorates a color purity of the picture. Of various vibration attenuation devices suggested for solving the shadow mask vibration, a method for bringing a damper wire into contact with the shadow mask for attenuation of the vibration for attenuation of the vibration is widely used. FIG. 1 illustrates a longitudinal section of a related art flat Braun tube having a damper wire applied to a shadow mask.
Referring to FIG. 1, the related art flat Braun tube is provided with a panel 1 forming a front face of the flat Braun tube, a fluorescent film 2 of red, green, blue dots coated on an inside surface of the panel 1, a funnel 3 welded to rear of the panel 1, an electron gun 5 sealed in a neck part 4 of the funnel 3 for emission of three electron beams 6, a deflection yoke 9 for deflecting the electron beams 6 emitted from the electron guns 5 in an up, down, left or right direction, a shadow mask 7 having a plurality of electron beam pass through holes 10 for passing the electron beams 6 selectively, a rail 8, a rectangular support, attached to an inside of the panel 1 for supporting the shadow mask 7 so as to exert a tension to the shadow mask 7, and a plurality of damper wires 11 each for strapping the shadow mask 7 through a portion of the shadow mask 7 between the electron beam pass through holes 10 under a tension with each end fixed to one side of the rail 8.
FIG. 2 illustrates a section across line Ixe2x80x94I in FIG. 1 for showing a relation between the damper wire and the shadow mask, and FIG. 3 illustrates a section across line IIxe2x80x94II in FIG. 2 for showing how the damper wire 11 attenuates vibration of the shadow mask 7.
Referring to FIG. 2, the damper wire 11 is in contact with the shadow mask 7 over an entire length of the damper wire 11 in parallel to a vertical side of the rail 8. And, the tension of the damper wire 11 is set stronger than the shadow mask 7. It means that a natural frequency of the shadow mask 7 is lower than a natural frequency of the damper wire 11 according to an equation (1) shown in the detailed description of preferred embodiments of the present invention. Therefore, as shown in FIG. 3, when a vibration is transmitted from the flat Braun tube, the damper wire 11 vibrates faster than the shadow mask 7. The difference of vibration between the shadow mask 7 and the damper wire 11 causes the shadow mask 7 and the damper wire 11 to collide to each other, by which the vibration of the shadow mask 7 is attenuated. The tension of the damper wire 11 is set stronger than the same of the shadow mask 7, for exerting a stronger resistance to the shadow mask 7 when the shadow mask 7 hits the damper wire 11 during vibration to attenuate the vibration, effectively. However, excessively strong damper wire tension breaks the damper wire 11, thereby dropping a Braun tube production efficiency.
Accordingly, the present invention is directed to a damper wire for a shadow mask in a flat Braun tube that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a damper wire for a shadow mask in a flat Braun tube, which has a weak tension for prevention of breakage of the damper wire, but still can enhance an attenuation efficiency.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the damper wire for a shadow mask in a flat Braun tube includes a shadow mask, a support for supporting the shadow mask under a tension, a damper wire fitted to the support in contact with a surface of the shadow mask, wherein, the damper wire satisfies a condition expressed in an equation, T less than xcfx80xcfx81L2f2n-s/m, where T denotes a tension of damper wire, xcfx81 denotes mass per unit length of the damper wire, L denotes a total length of the damper wire, and fn-s/m denotes a first natural frequency of the shadow mask.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.